The invention relates generally to a system and method for operating a turbo-charged compression-ignition engine and, specifically, to a system and method for substantially reducing specific fuel consumption and engine exhaust emission in a turbo-charged engine. More specifically, the invention relates to a system and method for enabling a uniform exhaust gas recirculation to different cylinders in a multicylinder engine.
In a compression-ignition engine, such as a diesel engine, a fuel injection system injects fuel (e.g. diesel fuel) into compressed air within each of the engine cylinders to create an air-fuel mixture that ignites due to the heat and pressure of compression. Unfortunately, engine efficiency, power output, fuel consumption, exhaust emissions, and other operational characteristics are less than ideal. In addition, conventional techniques to improve one operational characteristic often worsen one or more other operational characteristic. For example, attempts to decrease specific fuel consumption often cause increases in various exhaust emissions. Vehicle exhaust emissions include pollutants such as carbon monoxide, nitrogen oxides (NOx), particulate matter (PM), and smoke generated due to incomplete combustion of fuel within the combustion chamber. The amount of these pollutants varies depending on the fuel-air mixture, compression ratio, injection timing, ambient conditions, and so forth.
Stringent emission regulations have forced emissions from engines to reduce over the years. One of the emissions of concern is nitrogen oxide (NOx) emissions. Exhaust gas recirculation is one of the potential ways to achieve low NOx emission levels. Exhaust gas recirculation involves pumping a fraction of exhaust gas into an air intake manifold, which is at a higher pressure than an exhaust manifold pressure. As a result, exhaust gas recirculation requires a means for pumping the exhaust gas into the intake manifold. Conventionally means for pumping may include convergent nozzles (venturies) and externally driven pumps/blowers. The usage of additional components for recirculation of exhaust gas increases specific fuel consumption (SFC) of the engine. Also, conventional exhaust gas recirculation systems do not enable a uniform exhaust gas recirculation to different cylinders in a multicylinder engine.
It is desirable to have a system and method that enable a uniform exhaust gas recirculation to different cylinders in a multicylinder engine and also substantially reduces specific fuel consumption and engine exhaust emission in a turbo-charged engine.